Often web & database searches will lead you to specific product information such as market share or size. Try searches such as:
("market share" OR "market size" OR sales OR "units sold") AND (iPhone OR droid OR android)
TIP: Follow up on market research firms mentioned to find additional information or press releases which may have more detail.
Dig deeper to find product specific information:
Web Searching: Use synonyms
(distribution OR alliances OR partnerships OR vendors OR "marketing channels") AND (iphone OR smartphone)
Try also specific partners:
AT&T iPhone distribution